Judging crowds’ size by ear and by eye in virtual reality

Abstract

Judging the size of a group of people is an everyday task, on which many decisions are based. In the present study, we investigated whether judgment of size of different groups of people depended on whether they were presented through the auditory channel, through the visual channel, or through both auditory and visual channels. Groups of humanoids of different sizes (from 8 to 128) were presented within a virtual environment to healthy participants. They had to judge whether there was a lot of people in each group and rate their discomfort in relation to the stimuli with Subjective Units of Distress. Our groups of 96 and 128 virtual humans were judged as crowds regardless of their sensory presentation. The sensory presentation influenced participants’ judgment of virtual human group size ranging from 8 to 48. Moreover, while the quantity judgments in the auditory condition increased linearly with the group size, participants judged the quantity of people in a logarithmic manner in the two other sensory conditions. These results suggest that quantity judgment based on auditory information in a realistic context may often involve implicit arithmetic. Even though our participants were not phobic of crowds, our findings are of interest for the field of virtual reality-based therapy for diverse disorders because they indicate that quantity judgment can potentially be altered in a sensory-specific manner in patients with fear of crowds.

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Acknowledgments

This research was supported by the EU FP7-ICT-2011-7 project VERVE (http://www.verveconsortium.eu/), Grant no 288910. This work was performed within the Labex SMART (ANR-11-LABX-65) supported by French state funds managed by the Agence Nationale de la Recherche within the Investissements d’Avenir programme under reference ANR-11-IDEX-0004-02. The research leading to these results has also received funding from the program “Investissements d’avenir” ANR-10-IAIHU-06. We thank Thibaut Carpentier and Kévin Perros for their work on the elaboration of the auditory component of the virtual environment. We thank Camille Frey and Cassandra Visconti who contributed to the experimentation.